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I guess I'm crazy, I love my 74 60/6... It's got it's own heart.... I also have a 75 60/6, that was a barn find only 14,400 miles on it, was sitting for so long I've decided to do a semi-total restore,,,,just haven't told the wife yet it's definently a love affair.

Not the best weekend in the shop. I did get the EBC brake rotor on, which allowed me to clean and lube the wheel bearings, and I rebuilt the master cylinder and brake caliper. The wheel bearings were nasty. The grease was hard and the bearings were a bit rusted, but still working. Those may get replaced in the future, but for now I cleaned them up and got the wheel back on. I used the Mobile 1 synthetic wheel bearing grease.

The real bummer was that once I got things back together, I noticed fluid dripping out of the master cylinder at the piston opening. The inside of the cylinder was just too pitted and corroded to work with the new seals. I took it off and I'm sending the core to Apple Hydraulics to re-sleeve the cylinder. The caliper wasn't so bad and seems to work well.

I need to get the rear wheel and swingarm off to service those parts, and get the transmission out to inspect and lube the clutch. But I was beat from working too much, even though it's a labor of love, and it will have to wait for a while.

Here's the internals of the master cylinder rebuild. The piston on the right is the old corroded one, and the new one and associated parts on the left. But as I said, the bore in the body was just too far gone with corrosion.
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Things went better with the caliper. Here's the kit:
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And all clean and back together:
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The front wheel bearings were quite nasty.
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Everything cleaned up easily, and I use a wheel bearing cup to repack the bearings.
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Looking good and ready to go:
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One done, one to go:

The rear wheel is off and the bearings removed. One of the bearing races came out w/o heat, which is bad. They are supposed to be held in by the normal contraction of the heated hub around a frozen race, and then require heat to remove.

I read a lot about it on line, and I will use red locktite to glue in the race. But, this makes it close to impossible to remove the race in the future. Therefore, I'll buy new bearings since these are a bit used, pitted, and rusted. That way, once it is together, I should be done with it for the rest of its life, at least its life with me.

The drive gear on the wheel hub (that mates to the final drive gear) is worn. I think I will let it slide for now. They are still available for about $85 which is nice. If the trans and clutch work out well, and it runs well, I'll likely drop a new one on at that time. The teeth are getting pretty bad, I'll post a picture later.

Has anyone replaced this gear on the hub? I see it is riveted on. I can buy the rivets, too, but don't really have any means to use them. I was thinking proper diameter grade 8 bolts would work just as well. I figure if I mated the parts on the bike to hold the position, I could bolt the hub in place and use red locktite to make it permanent.

Here is the inner spacer on the lathe. I read that if you reduce the diameter a slight amount, it will go in and out without having to remove the bearing races. Since I don't want to remove them ever again, I did the reduction. Yeah, it's a wood lathe, but on low speed, for light metal, it works fine. It fit into the drive chuck perfectly, and the conical tail chuck holds it well and centered. I need to reduce the diameter of the two thin disc like ridges. The one on the left was too close to the head drive chuck so I put on an O-ring to push it away from the chuck so I could turn it down a fraction with the gouge. Worked perfectly. New bearings are on order and will have them by the weekend.

Wife wants to go to a Cirque du Soleil show, but all I want to do is be in the shop.

Fairing

If memory serves me correctly, the Luftmeister fairing uses the original BMW
headlight and chrome ring, the Windjammer uses a stock automotive headlight.
Also noted in the pictures, the fork brace has been replaced with an upgraded
model.
I would rebuild the forks, I would be willing to bet you'll find stuff inside them
you really don't want to see.

There is a rubber bumper for bottoming in the sliders, which has likely disintegrated into goo, plus little chunks trying to plug your damping rod holes. You will want to drop the sliders and clean all that up, both from damping rods and inside sliders.

IIRC correctly the soft service parts are the aforementioned bumpers; the fork seals; gaiters if yours are toast; large crush ring under that large bottom nut; tiny crush ring which goes on the end of the damping rod; possibly some little felt strips.

If the forks are currently working smooth, take note of all the washers/shims associated with attaching that fork brace to your sliders. It is a real PITA to shim these so your forks are smooth and stiction free; if that work is done make sure you reap benefits! There is no adjustment besides shimming.

Perfect time to install milled upper triple plate to replace that flimsy stock thing, if it has not alreeady been done.

I got the new bearings from Autozone for the rear wheel. I used my kerosine heater to get the hub hot, at least 200 degrees F, and the bearing assembly, held together with a long bolt, was put in the freezer. It dropped right into the hot hub w/o issue, and locktite glue was used to hold the outer race in place. New bearings were a good idea. The new bearings are just so nice and smooth. I should be able to completely assemble the rear wheel tonight and adjust the bearing preload.

The swing arm is about the only item on the bike that was in good condition. The bearings are great, and they were clean and lubed. They'll be going back in with new seals.

I also got the transmission out. The good news is that all the clutch parts look fine. At least good enough to not replace anything now. Clutch parts are not cheap, so this is good news. Also, the friction disc was very sticky on the transmission input spline, so I'm confident a good cleaning and spline lube will help with the shifting issues I was seeing.

Here' s one thing that drives me mad: poor quality, lazy workmanship. The last person to service the clutch put in one of the clutch bolts and stripped it badly. There was no way to get it out with an allen wrench. The internal hex hole was at this point almost round. The bolt was too tight (and seized?) for vise grips even though I had a decent purchase. I might have been able to use an Easy Out extractor, but the most simple solution was to use the MIG welder as the space was tight and the other bolts were REALLY tight and needed a lot of torque to break loose.

I got a proper sized bolt and MIG welded it to the exposed head of the stripped bolt and then it came out quite easily. I am thinking that the heat of the welding made the bolt easier to get out than the others. I have ordered 6 new bolts. I don't know if I will ever be in this area of the bike again, but at least the next guy who is won't have to deal with any poor workmanship on my part.

Here's a few pics:

This is the neutral switch on the trans. The wires are cut, which explains why the neutral light was not working!
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Whoo hoo, the trans is out!
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Here is the allen bolt on the clutch that is completely stripped:
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And the bolt I MIG welded to it to easily extract it. All six will go to the trash.

Good weekend for the R90. I made a clutch centering tool and got the clutch and transmission back in. I installed new seals in the swingarm and back it went. Finally, the final drive and wheel. The seals are VERY difficult to get started into the swingarm, even using a press. I almost messed one up beyond usage but I was able to salvage it.

Since I put new bearings in the wheel hub, I had to set the spacing and bearing preload. This was new to me, probably not for Airhead gurus on this board. This is done with an inner and outer spacer. The outer spacer sets the distance between the bearing races and is fixed. The inner spacer sets the distance between the center of the bearings (the part that spins with the axle). You change this distance with thin spacers until you have the proper preload. This is determined by rocking the rear wheel while a buddy (in this case, Brian!) tightens the axle. Once the wheel has no play in it, you check the torque. If it is around 25 ft-lbs, you're done. It took several tries to get it right, but we got it.

I still don't have a front brake (the master cylinder is being re-sleeved at Apple Hydraulics) but I still went out for a few miles. It's running great, just a few more things to wrap up, like the seat and hinges and the front brake. Once that is done, it's time to enjoy it for a while and then later in the year I'll take the front forks apart for a servicing and the steering head bearings.

Here's a picture of the parts of the wheel hub, spacers, bearings, etc. Everything but the grease seals. There's a hell of a lotta parts in the rear wheel hub!

Here's the centering tool I made on the wood lathe:
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Here it is ready for use. The size fits snugly into the clutch disc and the center tip falls into the dimple on the pressure plate. That centers the clutch disc so the transmission will go in properly.
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Here's the clutch back together, and centered. You have to use longer bolts, seen with the wood blocks, to compress the clutch spring disc. Then you can put in the proper smaller bolts and torque it down. It all worked really well.

You have to use longer bolts, seen with the wood blocks, to compress the clutch spring disc. Then you can put in the proper smaller bolts and torque it down. It all worked really well.

I didn't use wood blocks but used nuts and oversized washers run down to the back of the clutch pack. Then, using a wrench, I turned each nut about the same amount in succession. I went round and round the three nuts to evenly pull the spring down. Without the nuts/washers, you have to know rather precisely how thick to make the wood blocks. But in the end, it does the same thing.

The only reason I used wood blocks was because when I bought the bolts, I forgot to measure the correct size. I got 2.5 inch bolts to be safe, then had to make up the difference with the wood blocks. Would have done it your way if I had planned better!